The majority of quilting patterns will use imperial measurements (inches, "), some will also convert to metric (centimeters, cm).
When you are piecing blocks together you will need to sew them with a 1/4" seam allowance (0.6cm).
When you have been piecing for a while you can probably sew 1/4" by eye. Until then you will want to mark the back of your fabric to make sure you are getting that accurate seam allowance.
You can use your quilting ruler and a fabric pen that will show up on your fabric (you could use a pencil since the mark will be on the back of your fabric).
Line up the edge of your fabric with the 1/4" line on your ruler and draw a line along the fabric.
Move your ruler to the next edge and draw another line.
Carry on marking your 1/4" in this way until you have marked all of your seam lines.
You can now place your fabrics right sides together and sew an accurate 1/4" seam allowance.
There are tools you can buy, rather than using your ruler, such as Prym's 'Quilter's Quarter' or Simplicity's 'Quarter Inch Seam Ruler'. If you need to add a 1/4" to a curved piece you can use Sew Easy's 'Magic Seam Marker' or Jen Kingwell's 'Simple Seam Wheel'. You could even try a 'quilter's flexible curve'.
Happy Stitching